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Installing the underlayment for a floating floor is one of the most important processes of the floor installation. The underlayment cushions the floor, thus preventing bends and cracks, and it also protects against moisture. These two functions are combined in plastic-coated foam underlayment, available from most laminate flooring dealers. If you want to lay down uncoated foam, you have to cover the subfloor with polyethylene sheeting first. For the warranties on your underlayment and flooring to be valid, the subfloor must be level within specified limits.

1

Level the subfloor to the specifications detailed on the installation directions for your flooring. Use floor-leveling compound to fill depressions and a belt sander to knock down high points. Vacuum the floor when you're done.

2

Remove the baseboard from the entire perimeter of the room with a pry bar. Cut the bottoms of the door jambs to the height of the new floor with a hand saw. Use a spare piece of flooring and underlayment as a guide to mark the cut line.

3

Lay 4-mil or thicker polyethylene sheeting over the entire floor if you're using uncovered foam underlayment. Overlap the edges of the plastic 8 to 10 inches and staple it to the floor with a staple gun. Omit this step if you're using two-in-one underlayment that includes both foam and a plastic coating.

4

Lay the first row of foam along the wall against where you plan to start installing the flooring. Stretch it from one end of the room to the other, cut it to size with a utility knife and remove the tape on the underside to expose the adhesive strip. Press down to secure it to the floor.

5

Begin installing the flooring after laying the first row of underlayment. When the boards are within 6 inches of the outside edge of the underlayment, lay another strip. If you're using a two-in-one product, overlap the plastic by 8 to 10 inches. Butt the edges of the foam together, however, with no overlap.

6

Continue installing underlayment and flooring until you reach the opposite wall. Cut the last row of underlayment to fit with a utility knife.

Things You Will Need

Floor-leveling compound

Belt sander

Vacuum

Pry bar

Hand saw

Polyethylene sheeting

Staple gun

Utility knife

Tips

The adhesive on the underlayment isn't very strong. It is only intended to hold the material down until you lay flooring over it.

Underlayment also functions as a sound barrier between floors. If this is a priority for you, consider choosing cork underlayment, which has more ability to dampen noise than foam.

About the Author

Chris Deziel has a bachelor's degree in physics and a master's degree in humanities. Besides having an abiding interest in popular science, Deziel has been active in the building and home design trades since 1975. As a landscape builder, he helped establish two gardening companies.